Question

cos 55° cos55° + sin55° sin 55° - ctg 45° вычислить

Answer 1

$\cos(55°) \cos(55°) + \sin(55°) \sin(55°) - \cot(45°) = \\ = \cos {}^{2} (55°) + \sin {}^{2} (55°) - \cot(45°) = \\ = 1 - \cot(45°) = 1 - 1 = 0$